A metabolite of 24-epi-brassinolide in cell suspension cultures of Lycopersicon esculentum

Tomato cytochrome P450 CYP734A7 functions in brassinosteroid catabolism

“…Previous feeding experiments with 24-epi-BL 4 suggested the presence of P450s catalyzing hydroxylation at either C-25 or C-26 in tomato suspension cells (Schneider et al, 1994;Hai et al, 1995;Winter et al, 1997). Scanning the tomato EST database (http://tigrblast.tigr.org/tgi/) resulted in the identification of several CYP734A clones.…”

“…Although published results indicate that BRs exogenously applied to plants are rapidly metabolized (Yokota, 1999), very little is known about the enzymes involved in the catabolism of endogenous BRs. Exogenous applications of radiolabelled 24-epi-castasterone (24-epi-CS) and 24-epi-brassinolide to cell suspension cultures of Ornithopus sativus (Kolbe et al, 1996) and tomato (Schneider et al, 1994;Hai et al, 1995;Winter et al, 1997;Kolbe et al, 1998) revealed that a variety of modifications of the BR molecules occur (Fig. 1).…”

Brassinosteroid phytohormones: structure, bioactivity and applications

“…24-Epibrassinolide (6; figure 14) was transformed to the glucopyranosides 118 and 119, while 25-hydroxy-24epibrassinolide (120), obtained by enzymatic hydrolysis of 118, was transformed exclusively to the 25-glucoside 118 in cultured cells of tomato (Schneider et al, 1994;Hai et al, 1995). These hydroxylations are performed by two distinct enzymes, and 25-hydroxylase proved to be a cytochrome P450 protein, while the 26-hydroxylase seems to be a flavin-containing monooxygenase (Winter et al, 1997).…”

Brassinosteroids

“…Most of the studies on BR metabolism have been in species other than Arabidopsis (Adam and Schneider, 1999). In cell suspension cultures of Lycopersicon esculentum, 25-hydroxy-24-epibrassinolide and 25-β-D-glucosyloxy-24-epibrassinolide constituted the major radioactive BRs seven days after feeding with [ 3 H]-24-epibrassinolide (Schneider et al, 1994). Further studies with [ 3 H]-24-epicastasterone showed that tomato cells metabolized this BR not only to the 25-hydroxy form but also to 26hydroxy-24-epicastasterone and 26-β-D-glucopyranosyloxy-24-epicastasterone, and the same system was used to show that direct glucosylation could occur at either of the hydroxyls in the A ring after epimerization (Hai et al, 1996).…”